Multiple-story, multiple-unit office and housing structures are constructed with concrete floors and slabs for structural stability and load-bearing capacity. Such concrete floors and slabs are typically provided with numerous various-sized superposed voids, cavities, holes and openings formed through multiple vertically aligned floors to enable the installation and supply of plumbing, electrical wiring, electronic cables, heating and cooling ductworks and other required and desired services and amenities to each floor. Concrete floors poured for multiple-story structures require precise positioning and superposed alignment of such voids, cavities, holes and openings to enable convenient and efficient positioning of water supply and waste removal pipelines, and wiring conduits from the bases of the structures to their top floors, and are formed by the precise positioning, aligning and securing of hole-forming devices to construction baseplates onto which concrete is poured, finished and set to form the floors and slabs. Hole-forming devices for these purposes are well-known and are commonly referred to as pipe sleeves or canning sleeves or cores.
Present day skyscraper and super-skyscraper building structures are provided with service rooms to house electrical, plumbing and heating/cooling substations on located on multiple floors interdispersed along the vertical height of the building structures. Concrete floors on which such service rooms are installed, must be provided with thicker depths in order to support the added weights of service equipment. The thicknesses of concrete floors bearing substation service rooms must confirm to local building codes and can vary between 12″ to 20″ depending on local regulatory requirements as compared to thickness of non-service concrete floor requirements of 8″ to 12″. Numerous types of stackable telescoping pipe and canning sleeves have been developed to provide hole-forming devices that can be used to form voids, cavities, holes or openings in concrete floors of different thickness thereby making it possible for a single type of a device to be used on a job site. The prior art telescoping pipe and canning sleeves are commonly manufactured with plastics material for economy and ease of portability and use. However, such plastic telescoping pipe or canning sleeves are commonly collapsed or deformed or displaced by biasing, compressive and torsioning forces caused by the dispensing, distribution and setting of wet concrete onto baseplates whereon the telescoping sleeves were installed. The resulting misaligned and mis-positioned voids must be repaired, i.e., repositioned by boring or drilling or jack-hammering into the set concrete floors. Consequently, the preferred hole-forming devices currently favoured in building construction are single-length units manufactured by sectioning PVC pipe into selected lengths. Although such PVC hole-forming devices are durable, multiple lengths are required in order to provide voids, cavities, holes and openings through floors of different thicknesses.